What is Abductive Reasoning?

Legal Definition
Abductive reasoning (also called abduction, abductive inference or retroduction) is a form of logical inference which goes from an observation to a theory which accounts for the observation, ideally seeking to find the simplest and most likely explanation. In abductive reasoning, unlike in deductive reasoning, the premises do not guarantee the conclusion. One can understand abductive reasoning as "inference to the best explanation".

In the 1990s, as computing power grew, the fields of law, computer science, and artificial intelligence research spurred renewed interest in the subject of abduction. Diagnostic expert systems frequently employ abduction.
-- Wikipedia
Legal Definition
A reasoning methodology that uses common facts that are accepted as true and using them to build your argument.